Coin discriminator

ABSTRACT

A method of categorizing coins/tokens by energizing detect coils with a single pulse detecting the back EMF curve of the decaying pulse information, analyzing the unmodified back EMF curve to extract therefrom a number of variables and processing those variables to provide values proportional to the variables, and comparing the values of the coin/token to at least one of a number of reference values to determine into which of a number of predetermined categories the coin/token falls.

FIELD OF THE INVENTION

This invention relates to a method and apparatus for discriminatingbetween coins, tokens or similar articles.

BACKGROUND OF THE INVENTION

Coin-operated apparatus are being increasingly used throughout the worldto provide goods and services. Such apparatus includes amusementmachines, vending machines for a wide variety of products, gamingmachines (such as "poker machines") and pay phones.

As a sub-group, vending machines dispensing such varied products aspublic transport tickets, confectionery, video cassettes and breadsticks are increasingly apparent in developed countries due to the highcost of labour and a demand for twenty-four-hour access to suchproducts.

In addition, public telephones or pay phones are becoming moresophisticated. Although there is a trend towards pay telephones whichoperate only on a debit card or credit card, it is likely that futurepay telephones will be modelled on those currently in use in Italy, inwhich one may use coins, cards or gettoni (telephone tokens).

Although there are in use banknote validators, the problems inherent in"reading" banknotes (particularly mutilated or worn banknotes) coupledwith the trend in most countries to replace lower denomination banknoteswith coins, means that in all of the abovementioned applications, a coinvalidator will be required.

To be acceptable in one of the abovementioned applications, a coindiscriminator must quickly and accurately discriminate between coins ofdifferent denomination, between coins of different countries and betweengenuine coins and bogus coins. Existing coin discriminators have beenunable to discriminate adequately, in some cases, between a low valuecoin of a foreign country and a higher value coin of the country inwhich the validator is located. Particularly in a region such as Europe,coin discriminators additionally cannot cope with the large number ofmigratory coins from various European countries.

One example of a prior art coin validator is provided by U.S. Pat. No.3,918,565, which discloses coin selection methods and apparatus in whichdata representative of a coin is compared with data stored in aprogrammable memory.

In U.S. Pat. No. 3,918,565, a numerical value of a signal produced byinterrogating a coin, such as frequency, is compared with acceptablenumerical values for genuine coins which are stored in the programmablememory.

Another prior art coin validator is disclosed in AU-B-24242/84, whichdiscloses the use of pulsing coils which induce eddy currents in a coin.Monitoring means is used to monitor the decay of the eddy currents, anda comparison between the output of the monitoring means and storedreference values enable discrimination to take place. It is consideredthat the approach of AU-B-24242/84 is unnecessarily complicated, andwould not permit an adequately rapid discrimination to take place.

In U.S. Pat. No. 5,020,652 to Shimizu there is disclosed a device fordiscriminating between different coins, such a real or counterfeitcoins, without contacting the coins. Shimizu uses a coil to provide apulse of a magnetic field into the coin, and then detects the decayingcurve of the back EMF created by the eddy currents in the coin. Thecharacterstics of that decaying curve are determined by the material ofthe coin, its diameter and thickness, and any surface treatment.Therefore, for non-identical coins, the decaying curves are alsonon-identical.

After detecting the decaying curves Shimizu then subjects the decayingcurve to series of manipulations prior to comparing the characteristicsof the decaying curve with the known characteristics for known coins.Those manipulations include the use of a switched-gain amplifier, and ananalogue-to-digital converter. Also, Shimizu uses a binary counter todetermine the end of each cycle so the amplification factor can beincreased for the following half cycle.

This creates an analysis regime which is unnecessarily complex. It alsomeans that the inherent characteristics of the decaying curve are notused, but rather a digital signal derived from a modified form of thecurve. In this way, certain inherent characteristics of the coin beingtested may not as accurately be determined. Furthermore, with Shimizu,an amplified and digitised representation of the decaying waveform isfed into the microprocessor for direct comparison with the knownwaveforms of particular coins.

In Australian Patent Application No. AU81826/91, another approach isdisclosed using pulsing of coins. In particular, it included the stepsof, (i) energising detect coils, with a single pulse, between which atleast part of a coin is located, (ii) extracting from at least oneportion of the back EMF curve of the decaying pulse information toprovide a definition of the coin, each portion of said back EMF curvebeing inverted and amplified, and (ii) comparing in a microprocessor thedefinition of the coin with a reference definition, to determine whetherthe coin is acceptable or unacceptable. The definition is in the form ofa period of time, or a number of system clock counts, which countsrepresent a period of time. The period of time relates to the timebetween a predetermined time, between the de-energisation of said coils,and the intersection of said back EMF curve with a reference voltage.

The inversion and amplification of the back EMF curve was required toproduce a measurable signal capable of properly being used forvalidation purposes. However in so manipulating the curve, its abilityto discriminate between extremely similar coin types is diminished.

Further investigations have been directed to optimising this type ofdiscrimination method with emphasis on the significance of the back EMFoscillation curve.

DESCRIPTION OF A PREFERRED FORM OF THE INVENTION

In one preferred form of the invention an unmodified back emfoscillating waveform from a single pulse of a token/coin is used toprovide information for discriminating coins/tokens. The unmodified backemf oscillating waveform is of increased significance in discriminationas it does not have important distinguishing characteristics excluded bysubsequent manipulation of the type currently known. Preferably, and indirect contrast to Shimizu, from the unmodifed decaying wave areextracted a number of variables which are processed to provide valuesproportional to those variables, with those values being fed into amicroprocessor for comparison with the corresponding values of thosevariables for coins of known denomination stored in the microprocessorto enable the category of the coin under test to be determined.Advantageously, the values are time values.

In particular, an improved method of coin/token discrimination ispossible by non dampening of decay oscillation of the detect coil field.Such reference data being assembled on the basis of the unmodifiedoscillating waveform can be representative of a particular type ofcoin/token to the exclusion of very similar other coins/tokens.

Particularly characteristic data may be extracted from the unmodifiedback emf oscillating waveform to enhance discrimination betweencoins/tokens. Such characteristic data for a coin/token may include:

(i) superimposing a mean amplitude curve;

(ii) the phase and/or change in phase of each oscillating waveform;

(iii)

(a) the curves plotted by the peaks of either or both of the positiveand/or negative portions of the oscillating waveform; and

(b) the amplitude of the negative and/or positive peaks of eachoscillating waveform;

(iv) the area of the curves beneath the peaks of each oscillatingwaveform;

(v) the frequency and/or change in frequency of each oscillatingwaveform;

(vi) the decay of peaks of each oscillating waveform in a predeterminedtime; and

(vii) any combination of the above.

Accordingly by analysing such details a refined signature can beattributed to a type of coin/token. By allowing appropriate variation,it is possible to accurately discriminate between coins/tokens.

More specifically, the invention provides a method of validatingcoins/tokens, including the steps of:

(a) energising detect coils, between which at least a part of acoin/token is located, with a single pulse,

(b) detecting the back EMF curve of the decaying pulse information toprovide a definition of said coin/token, said back EMF curve beingsubstantially unmodified,

(c) comparing said definition of said coin/token with at least one of anumber of reference definitions to determine into which of a number ofpre-determined categories said coin/token falls.

DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will be illustrated in detail hereinafterwith reference to the accompanying drawings, in which:

FIG. 1 is an end elevation of an elevation of an embodiment of a coinvalidator body according to the invention;

FIG. 2 is a top plan view of the coin validator of FIG. 1;

FIG. 3 is an underneath view of the coin validator of FIG. 1;

FIG. 4 is an elevation of a subsidiary body element of the body of FIG.1;

FIG. 5 is a section along the lines 5--5 of FIG. 4;

FIG. 6 is an elevation of a main body element of the body of FIG. 1;

FIG. 7 is a section along the lines 7--7 of FIG. 6;

FIG. 8 is an enlarged view of part of FIG. 7;

FIG. 9 is a section along the lines 9--9 of FIG. 6;

FIG. 10 is a section along the lines 10--10 of FIG. 1;

FIG. 11 is a non dampened back emf oscillating waveforms of two coins Aand B;

FIG. 12 is a back emf oscillating waveform of coin A of FIG. 11 with anupper mean amplitude curve;

FIG. 13 is the signal of FIG. 12 with a lower mean amplitude curve;

FIG. 14 is the signal of coin A of FIG. 11 with upper and lower meanamplitude curves;

FIG. 15 is the signal of FIG. 14 with measurements after a first clockcount;

FIG. 16 is a back emf oscillating waveform with mean curves for afurther coin.

FIGS. 17 to 25 are examples of oscillating waveforms for differentcoins;

FIGS. 26 to 35 are graphic representations of the ability of theprincipal variables to distinguish the coin sets of FIGS. 17 to 25; and

FIGS. 36 is a circuit diagram illustrating one embodiment used toconduct the discrimination of the present invention.

In FIGS. 1 to 10, "hardware" aspects of a known validator is disclosedto which the invention may be applied.

As shown the coin validator is a self-contained unit locatable in aparticular apparatus, such that a coin introduced into theapparatus--whatever the apparatus may be--will travel past a detect coilin the validator, will be validated or invalidated, and as a consequencewill emerge from one outlet or another outlet of the validator, and theappropriate signal will be sent to the particular apparatus for furtheraction.

Referring firstly to FIGS. 1 to 3, the coin validator 10 of includes abody 12 which has two body portions 14 (main body) and 15 (subsidiarybody), which are hinged together, as shown at 18.

Within subsidiary body portion 16 there is a printed circuit boardassembly 98, and a cover 100 is secured to body portion 16 by screws orthe like, one of which is shown at 28 in FIG. 5.

Main body portion 14 has a printed circuit board assembly 102 locatedtherein, and a cover 104 is secured to body portion 14 by screws or thelike.

On printed circuit board assemblies 98, 102 may be located all theelectrical and electronic components to operate, monitor and control thevalidator 10.

Main body cover 104 is adapted to hook into slots (108,110) on main bodyportion 14, and as stated before may be secured via screws such as 106.

To secure validator 10 to or in apparatus such as a vending machine,pins 112, 116, 118 may be used to attach the validator 10 to a bracket(not shown) in the apparatus.

The upper view of the generally cuboidal body 12 (FIG. 2) shows a coinentrance 20, and the underneath view (FIG. 3) shows an `accept` outlet22 and a `reject` outlet 24.

Turning now to FIG. 4, 5 and 6, in particular FIG. 5, a coin path 26extends from inlet 20. The width W of the coin path is selected to bethe ninimum consistent with the thickness of the coins likely to beintroduced into the validator 10 the width W is 3.5 mm, to accommodatethe thickest known coin.

A first optical sensor 28 is located close to the start of coin path 26,the first part of which 30 is a downwardly inclined (FIGS. 4,5) and isangled from the vertical (FIG. 5).

In FIG. 5, the base 32 of the coin path portion 30 of the embodiment ofthe present invention has an inclination, relative to side wall 36. As acoin (for example small coin X shown in FIG. 5) is dropped into outlet20, it will fall to portion 30. Under the influence of gravity, it willroll down the incline of portion 30, but the lower periphery of the coinwill also slide down the lateral inclination of the base 32, as such apart of a lower peripheral edge of the coin will make point contact onbase 32, and will locate between the lower end of base 32 and the lowerend of side wall 34. This causes the coin, again under the influence ofgravity, to fall to the position shown in FIG. 5, where the topperipheral edges makes a point contact with side wall 36 of coin path26. Successive coins passing through area 38 on coin path 26, will eachadopt an orientation where point contact will be made between aperipheral edge and wall 36, and a peripheral edge and base 32. Thisorientation is more stable and thus more reproducible in successivecoins passing through region 38.

Coin Y, being a larger-diameter coin, will have a slightly differentrest angle to that of coin X, but the angle is substantially the samefor all coins. This has been found to assist in accurate validation,different coins may adopt different orientations at the area 38 ofinterrogation (to be described hereinafter) through rattling or wobblingas they pass the area, or as a result of the coins being wet or sticky,which leads to a reduction in accurate discrimination.

Located on respective sides of coin path 26 at area 38 is one set ofinductive (pot) coils 40,42. Coils 40,42 are connected in a detectcircuit (such as, for example, the circuit of FIG. 11) and form asingular inductive field. The coils (40,42) are adapted to be energisedwith a single pulse, for each coin validation operation, by a generallyconventional switching circuit (not shown).

The coils 40,42 are physically connected to respective body portions14,16 preferably with an adhesive. From FIG. 5 it can be seen that thecoils 40,42 are located generally parallel to the plan of coin path 26,and as near as practicable are separated by about the coin path width W.

Located just adjacent to coils 40,42 in a position on the edge of thedetect area 38, is a pair of optical sensors 44,46 (FIGS. 4, 6 and 7).

In FIG. 7 there is also shown a reject lever 48, which may be pusheddown to release a jammed coin entering coin path 26.

Located at the base of body portion 14 is a coin accept/reject mechanism50, shown in more detail in FIG. 8.

The mechanism 50 provides a fast acting means for allowing an accepted,that is, a validated coin to move into an `accept` channel, whilstpreventing a rejected coin from passing into the accept channel. Therejected coin is diverted into a `reject` channel.

The mechanism 50 includes an accept/reject arm 62 which is pivoted on a`floating` pivot 64, to be activated by a solenoid which has a U-shapedelectro magnet 52 secured to body portion 14 by a screw or the like 54.The floating pivot 64 is adapted for limited movement, for example, itmay be located in a groove in portion 14, to facilitate rapid movementof arm 62 between positions.

Arm 62 is normally held by spring means 58 in the `reject` positionshown in FIG. 7, where surface 84 of the arm 62 constitutes acontinuation of base 32 of coin path 26.

When the mechanism is provided with an `accept` signal, instruction orthe like, the solenoid is energised. This causes arm 62 to be attractedto magnet 52. In particular, pivot 64 is attracted to the lower portionof magnet 52, eventually making contact therewith. At that stage themagnet 52/arm 62 combination enables more magnetic flux to be generated,and thus more magnetic force is applied to arm 62, to move it morequickly to the FIG. 8 position. It has been found that such anarrangement as the one shown in FIG. 8 enables extremely rapidretraction of arm 62.

The paths of both accepted and rejected coins will now be described inrelation to FIGS. 1 to 10; they are best represented visually in FIG.10.

FIG. 9 shows the body 12 of validator 10 in its open configuration,where body portions 14, 16 have been pivoted apart at pivot points 18.Pivot point 18 is preferably constituted by two hinge pins located ateither end of the body 12, generally on the line of the coin path 26.

The body portions 14, 16 and covers 98,102 are produced from a plasticsmaterial by injection moulding, and the coin path 26 is defined byinternal mouldings of the portions. Thus, the one `wall` of the coinpath 26 is formed on one portion, and the other `wall` on the otherportion.

The hinged body arrangement, best shown in FIG. 9, enables the twoportions 14,16 to be pivoted apart. The two portions are biasedtogether, by spring means or the like--in order that the coin path 26may be cleaned. Coin paths in validators often become dirty and/orclogged, due to residues carried by coins which pass therethrough.

Furthermore, the portions 14 and 16 are pivoted apart in order that bentcoins or slugs stuck in the device are able to drop free into the rejectpath.

The covers 98,102 fitted to body portions 14,16 also provide splash anddirt protection for the electronic components.

A coin Z--in the representation of FIG. 10, an Australian fifty-centcoin--enters validator 10 through inlet 20. There is in use, a coinchannel leading from outside a vending machine, for example, to inlet20, through which the coin Z may initially have to pass.

When the coin Z reaches the position shown, in which it is between coils40 and 42, (S1,S2 of FIG. 36) (see also FIG. 5, where coins X, Y areshown in that position) the presence of coin Z will be detected byoptical sensors 44,46 (S9 FIG. 36).

A `coin detected` signal from sensors S9 FIG. 36 44,46 is sent to amicroprocessor S8 FIG. 36 which causes coils 40,42 (S1,S2 FIG. 36) to beenergised with a single pulse. After analysing the results of thatenergisation or pulse, the microprocessor either sends or does not sendan `accept` signal to mechanism 50 (S10 FIG. 36).

If an `accept` signal is sent to mechanism 50, the solenoid will beenergised, arm 62 will be retracted, and coin Z will pass along the`accept` channel, marked by the arrowed line 86.

If the analysis rejects the coin, arm 62 will stay in the `reject`position and coin Z will be deflected by surface 84 of arm 62 into the`reject` channel shown by arrowed line 88.

Two further pairs of optical sensors are provided. They are checkoptical sensors 90,92 and accept optical sensors 94,96 (S9 FIG. 36).

If coin Z is accepted, and keeps moving down the accept channel, it willfirst pass between check sensors 90, 92. Both the check and acceptoptical sensors are continuously monitored by the aforementionedmicroprocessor so as to ascertain the direction of movement of a coinwithin the validator 10. If the passage of the coin Z is such so as totrigger the accept optical sensors (90,92) before triggering the checkoptical sensors (94,96) then the passage of the coin Z is considered tobe fraudulent and an alarm signal is generated or alternatively nooutputs will be generated. This applies in cases where a coin on a pieceof string or twine or other device is pulled in and out of the validatorin an attempt to create fake credits.

The coin continues down the accept path until it reaches the acceptoptical sensors (92). Upon triggering the accept optical sensor themicroprocessor considers that the coin Z has successfully travelledthrough the device and will give the appropriate outputs.

The approach of the present invention to coin validation/discriminationdata used in the validator 10 of FIGS. 1 to 10, will now be described.

In FIG. 11 the unmodified back emf oscillating waveforms of 2 coins (Aand B) are given and superimposed one on top of the other. These twodifferent coins were selected because of their close characteristicswhich makes them difficult to differentiate using current discriminationsystems.

Modification of these back emf oscillating waveforms by known means suchas inversion and amplification have tended to eliminate distinguishingfeatures between them, though of course, allowing ready discriminationwith other types of coins with clearly different characteristics.

As will be readily apparent from FIG. 11, the superimposed oscillatingwaveforms whilst initially very similar, display significantly differentamplitude and frequency after a relatively short period of time. Byrecording these differences for any type of coin it is possible todiscriminate even between very similar coins. The recordal can be by anysuitable means e.g. devising a resultant analog signal.

To compare these types of oscillating waveforms it is possible tomeasure and record various characteristics of the curves. For examplesuch characteristics, or variables include:

(i) superimposing a mean amplitude curve see FIGS. 12 to 14!;

(ii) the phase and/or change in phase of each oscillating waveform;

(iii) (a) the curves plotted by the peaks of either or both of thepositive and/or negative portions of the oscillating waveform; and

b) the amplitude of the negative and/or positive peaks of eachoscillating waveform;

(iv) the area of the curves beneath the peaks of each oscillatingwaveform;

(v) the frequency and/or change in frequency of each oscillatingwaveform;

(vi) the decay of peaks of each oscillating waveform in a predeterminedtime and

(vii) any combination of the above.

Some of these approaches are illustrated in FIGS. 12 to 16.

The area of curves beneath the peaks of each oscillating waveform hasthe advantage of allowing for variations in waveforms due to variationsin characteristics of coins of the same denomination. By taking the areabeneath the peaks any variations in waveform due to variations in coincharacteristics will be allowed for and consistent results obtained.

In FIGS. 12, 13 and 14 the back emf oscillating waveforms of a singlecoin is shown. Mean curves are drawn on the positive oscillationwaveforms amplitudes, negative oscillation waveform amplitudes and bothrespectively. Typically an analog signal for any of these waveforms canbe established to provide a signature for the particular type of coin.

FIGS. 15 and 16 show other characteristics of the back emf oscillatingwaveform of a single coin which can be used. For example in FIGS. 15 and16 different mean points of time are established for when theoscillations have dissipated to a predetermined amount.

If one considers the variables mentioned above in a specificcombination, it is possible to discriminate between coins having verysimilar characteristics.

By use of a circuit which can functionally be defined as:

    V(t)=Ae.sup.-σt sin (ωt+φ)+Be.sup.-αt

("the formula")

where:

V(t) is the voltage at time t

A is the amplitude of the oscillation waveform

B is the amplitude of the direct current component

φ is the phase angle of the response triggering delay

ω is 2πƒ

ƒ is the frequency of oscillation

σ is the decay associated with the oscillating waveform

α is the decay associated with the direct current component,

one can subject a coin with a single pulse, consider the results of thatpulse, and compare with the known data for known coins.

An analysis of captured data for a series of 34 coins is included inTable 1 below. In this analysis a curve-fitting program has been used tofit the captured data to the formula. This data represents the averagedata for a large set of captured samples, for example, 100 of each cointype. The spread of the calculated variables from the samples iscalculated as a Standard Deviation ("SD") expressed as a percentage. Inthe table "Sigma" is σ in the formula, and "Alpha" is α in the formula.

It is clear from Table 1 that A, σ (Sigma) and ƒ are three significantvariables. B and α (Alpha) are relatively minor terms with a high rangeof spread. The utilisation of these additional two variables will allowfor a higher degree of selectivity of coins, and improved accuracy. Aand B may not be distinguished, if required. Also, σ and α may not bedistinguished. The net effect of the combination of A, B, σ and α may beconsidered.

Therefore, by considering each of the variables alone, or in anycombination, the back EMF of a coin can be compared with known criteriaand its nature determined.

An example of the oscillating waveform, together with the curve A e⁻σt,and 10 times Be⁻αt, for each of the coins numbered 1, 2, 3, 5, 7, 9, 11,13 and 15 respectively, is shown in FIGS. 17 to 25. The "noise" curvealong the axis is a plot of 10 times the difference between the measuredvalue and the calculated value from the curve. After taking into accountthe 10 times multiple, it is clear the curve fitting has resulted in ahigh degree of fit between measured and calculated values.

FIGS. 26 to 35 show a series of graphic representations that demonstratethe ability of the principal variables A, ƒ, σ (Sigma), B and α (Alpha)to distinguish the various coin sets. The ability of each variable todistinguish one coin from the other is demonstrated by plotting onevariable against the other variable for the coin sets. These plots arebased on using these variables. Overlaps of the rectangles indicates alack of clear discrimination. Total discrimination is achieved by usingmore than one variable.

To achieve an equivalent to the combined effects of A/B, integration ofthe waveform for an odd number of half-cycles should be performed as theintegration of the odd number of half waves is proportional to themagnitude of the first half cycle waveform. Integration of an evennumber of half-cycles is a measure of σ/α as the difference between thefirst and second half cycle provides an indication of the rate of decayof the waveform. The measurement of the period for a number of cyclesprovides and indication of the frequency, ƒ.

This methodology has been demonstrated to produce a high level ofdiscrimination of the World Coin Sets.

To refer now to FIG. 36, there is shown a circuit which can be used toconduct the discrimination referred to above.

Coils S1 and S2 are connected in series and are magnetically coupled.Capacitor S3 is connected across the coils at the points S11 and S21.

Energisation of the coils S1 and S2 is controlled by switch S4 which inturn is controlled by output O1 of microprocessor S8. Microprocessor S8makes the decision with respect to the coil energisation upon receptionof the trigger information from the optocouples block S9 through theinput I4, I5 & I6 of microprocessor S8.

After coil S1,S2 is switched off under the control of microprocessor S8it produces a back EMF oscillating voltage waveform.

The waveform is applied to the zero-crossing detector at point S21 andlogic circuitry S5 at point S51, to the half period waveform integratorS6 at S61 and to the decay integrator of the even number of half periodsS7 at S71.

The zero-crossing detector and logic current S65 produces three outputs.The outputs are as follows:

i) at output S52 a signal proportional to the half-period of theoscillating waveform;

ii) at output S53 a signal proportional to the even number ofhalf-periods of the oscillating waveform;

iii) at output S54 a signal proportional to the period of theoscillating waveform.

The half-period waveform integrator S6 integrates the input waveform S61for the duration that an output is present at S62 for the zero crossingsand logic circuit S5 which is present for an odd number of waveforms.

When S62 is deactivated a stored integrated signal in S6 is dischargedwith a predetermined time constant. The period of the discharge isproportional to the integration of the area under the curve of theoscillating waveform. That information is presented at output S63 to theinput I1 of the microprocessor S8.

The integration of an odd number of waveforms represents the combinedeffect of A and B of the formula.

At the same time the oscillating waveform is presented to S7 and S71 andthe signal is integrated for the period that S72 is active. Upon thedeactivation of S72, the remaining stored signal value in S7 isdischarged at a constant rate such that the period of discharge isproportional to the decay information of the oscillating waveform. Thissignal is presented at S73 to the microprocessor S8 at the input I2.

The integration of an even number of waveforms provides an indication ofthe combined effects of σ and α of the formula.

At the same time the zero crossing detector and logic circuit S5produces an output signal S54 proportional to the period of thefrequency of oscillation of the oscillating waveform. This signal ispresented at I3 to the microprocessor 58 at the input I3.

The microprocessor S8 compares the signals at I1, I2, and I3 with a database of stored values within the microprocessor S8 and establishes thevalidity and denomination of a coin against values stored into themicroprocessor from reference data.

If a match is found, output O2 of microprocessor S8 is activated andpresented to the output activation stage S10 at point S101.

It is to be realised that the actual number of waveforms considered isnot important, but the accuracy of the results is higher for some of thevariables by selecting a larger number of cycles of the waveform. Also,it is preferred that the determinations are made on the basis of time.When the initial pulse applied to the coils stops, the internal clock inthe microprocessor starts so that time, in the form of clock pulses, canbe measured. In the case of frequency, for example, when a predeterminednumber of half-wave crossings have occurred a signal is applied to themicroprocessor to note the number of clock counts. That number isproportional to the frequency of the waveform.

                                      TABLE 1                                     __________________________________________________________________________    Coin      Amp A                                                                             Frequ                                                                             sigma                                                                             Amp B                                                                             alpha                                                                             SD A                                                                             SD F                                                                             SD sigma                                                                           SDb                                                                              SD alpha                          Code      Volts                                                                             kHz U-Sec                                                                             Volts                                                                             U-Sec                                                                             %  %  %    %  %                                 __________________________________________________________________________    1 AUS-99-$2-01                                                                          1.906                                                                             23.02                                                                             143.6                                                                             0.108                                                                             99.9                                                                              0.28                                                                             0.19                                                                             1.42 4.8                                                                              21.1                              2 FRA-00-F1-01                                                                          1.917                                                                             23.201                                                                            103.6                                                                             0.101                                                                             141.5                                                                             0.32                                                                             0.11                                                                             1.12 7  17.5                              3 HK-00-$2-L1                                                                           1.688                                                                             26.051                                                                            73.5                                                                              0.21                                                                              44.2                                                                              0.66                                                                             0.47                                                                             0.59 2  12.2                              4 HK-00$2-H1                                                                            1.678                                                                             26.156                                                                            76.3                                                                              0.205                                                                             47.3                                                                              0.7                                                                              0.47                                                                             0.61 2.2                                                                              10.6                              5 HK-00-$5-L1                                                                           1.658                                                                             26.47                                                                             68.8                                                                              0.214                                                                             45.4                                                                              0.37                                                                             00.4                                                                             0.5  1.7                                                                              11.7                              6 HK-00-$5-H1                                                                           1.654                                                                             26.513                                                                            70  0.21                                                                              47.4                                                                              0.3                                                                              00.6                                                                             0.39 1.6                                                                              8.7                               7 MEX-02-$5-L1                                                                          1.94                                                                              22.627                                                                            117.4                                                                             0.112                                                                             86.4                                                                              0.29                                                                             0.14                                                                             1.16 4.5                                                                              25                                8 MEX-02-$5-H1                                                                          1.946                                                                             22.483                                                                            136.4                                                                             0.102                                                                             96  0.23                                                                             0.09                                                                             0.46 6.8                                                                              27.5                              9 MEX-02-$500-                                                                          1.655                                                                             26.554                                                                            63.8                                                                              0.236                                                                             38.9                                                                              0.4                                                                              0.16                                                                             0.74 1.4                                                                              13.1                              10                                                                              MEX-02-$500-                                                                          1.634                                                                             26.739                                                                            69.4                                                                              0.221                                                                             44.1                                                                              0.3                                                                              0.09                                                                             0.45 2.1                                                                              11                                11                                                                              MEX-02-$1-L1                                                                          2.103                                                                             20.769                                                                            276.6                                                                             0.043                                                                             103.2                                                                             0.15                                                                             0.06                                                                             1.19 11.8                                                                             66.6                              12                                                                              MEX-02-$1-H1                                                                          2.093                                                                             20.894                                                                            236.2                                                                             0.049                                                                             93.1                                                                              0.2                                                                              0.13                                                                             2.47 11.2                                                                             60.9                              13                                                                              MEX-02-20-L1                                                                          2.041                                                                             21.455                                                                            225.5                                                                             0.056                                                                             81  0.25                                                                             0.12                                                                             1.74 5.9                                                                              56.5                              14                                                                              MEX-02-20-H1                                                                          2.028                                                                             21.54                                                                             235.9                                                                             0.058                                                                             92.9                                                                              0.29                                                                             0.16                                                                             1.87 7.4                                                                              50.6                              15                                                                              AUS-02-05-L1                                                                          2.083                                                                             21.059                                                                            226.7                                                                             0.031                                                                             171 0.13                                                                             0.06                                                                             1.87 20.1                                                                             47.1                              16                                                                              AUS-02-05-H1                                                                          2.084                                                                             21.035                                                                            233.1                                                                             0.032                                                                             202.5                                                                             0.13                                                                             0.05                                                                             1.64 25.7                                                                             51.3                              17                                                                              AUS-02-10-L1                                                                          1.985                                                                             22.928                                                                            77.5                                                                              0.138                                                                             43.8                                                                              0.54                                                                             0.13                                                                             0.91 5.8                                                                              33.4                              18                                                                              AUS-02-10-H1                                                                          1.965                                                                             23.071                                                                            79.6                                                                              0.145                                                                             43.4                                                                              0.49                                                                             0.12                                                                             0.93 4.5                                                                              31.3                              19                                                                              AUS-02-20-L1                                                                          1.677                                                                             26.331                                                                            61.2                                                                              0.244                                                                             35.8                                                                              0.35                                                                             0.1                                                                              0.45 1.1                                                                              12.7                              20                                                                              AUS-02-209-H1                                                                         1.657                                                                             26.517                                                                            65.8                                                                              0.23                                                                              40.1                                                                              0.33                                                                             0.1                                                                              0.52 1.6                                                                              11.8                              21                                                                              AUS-02-50-L1                                                                          1.613                                                                             26.985                                                                            71.4                                                                              0.218                                                                             44.6                                                                              0.31                                                                             0.12                                                                             0.85 2.2                                                                              10.9                              22                                                                              AUS-02-50-H1                                                                          1.604                                                                             27.081                                                                            74.2                                                                              0.209                                                                             48.3                                                                              0.28                                                                             0.11                                                                             0.86 2.8                                                                              11                                23                                                                              AUS-02-$1-L1                                                                          1.697                                                                             25.696                                                                            112.5                                                                             0.135                                                                             99.3                                                                              0.24                                                                             0.09                                                                             0.45 5  13.7                              24                                                                              AUS-02-$1-H1                                                                          1.691                                                                             25.713                                                                            120.6                                                                             0.128                                                                             114.1                                                                             0.21                                                                             0.09                                                                             0.39 4.1                                                                              10.7                              25                                                                              AUS-02-$2-L1                                                                          1.921                                                                             22.662                                                                            181.8                                                                             0.094                                                                             112.3                                                                             0.22                                                                             0.1                                                                              0.73 7.9                                                                              27.1                              26                                                                              AUS-02-$2-H1                                                                          1.908                                                                             22.734                                                                            195.8                                                                             0.091                                                                             126.4                                                                             0.21                                                                             0.12                                                                             0.82 7.5                                                                              20.4                              27                                                                              UK-06-02-L1                                                                           1.648                                                                             26.267                                                                            208.4                                                                             0.077                                                                             339.9                                                                             0.24                                                                             0.11                                                                             0.64 9.2                                                                              13.9                              28                                                                              UK-06-02-H1                                                                           1.646                                                                             26.3                                                                              218.5                                                                             0.074                                                                             369.7                                                                             0.27                                                                             0.14                                                                             0.77 9.7                                                                              14.9                              29                                                                              CAN-02-$1-L1                                                                          1.804                                                                             24.654                                                                            85.8                                                                              0.117                                                                             102 0.32                                                                             0.12                                                                             1.13 6.5                                                                              15                                30                                                                              CAN-02-$1-H1                                                                          1.804                                                                             24.678                                                                            83.1                                                                              0.12                                                                              94.1                                                                              0.32                                                                             0.14                                                                             1.03 5.3                                                                              14                                31                                                                              FIN-02-M5-L1                                                                          1.771                                                                             24.845                                                                            100 0.153                                                                             71.9                                                                              0.34                                                                             0.14                                                                             0.69 2.4                                                                              14.4                              32                                                                              FIN-02-M5-H1                                                                          1.765                                                                             24.882                                                                            105.7                                                                             0.149                                                                             82.3                                                                              0.28                                                                             0.13                                                                             0.69 2.1                                                                              10.2                              33                                                                              FIN-02-M10-L                                                                          1.759                                                                             25.055                                                                            86.1                                                                              0.15                                                                              75.1                                                                              0.28                                                                             0.08                                                                             0.55 3.9                                                                              9.9                               34                                                                              FIN-02-M10-H                                                                          1.754                                                                             25.135                                                                            81.8                                                                              0.155                                                                             68.3                                                                              0.31                                                                             0.15                                                                             1.01 3.4                                                                              9.1                               __________________________________________________________________________

We claim:
 1. A method of categorizing coins/tokens, including the stepsof:(a) energizing detect coils, between which at least part of acoin/token is located, with a single pulse, (b) detecting the unmodifiedback EMF curve of the decaying pulse, (c) analyzing said unmodified backEMF curve to measure at least one characteristic of said unmodified backEMF curve, (d) comparing said at least one characteristic with thecorresponding characteristic(s) of a reference unmodified back EMF curveto determine therefrom into which of a number of predeterminedcategories said coin/token falls.
 2. A method as claimed in claim 1,wherein said at least one characteristic of said unmodified back EMFcurve includes any one or more of; the amplitude of the oscillating waveform, the amplitude of the direct current component, the phase angle ofthe response triggering delay, the frequency of oscillation, the decayassociated with the oscillating waveform, and the decay associated withthe direct current component.
 3. A method as claimed in claim 2, whereinthe amplitude of the oscillating wave form, the amplitude of the directcurrent component, the decay associated with the oscillating waveform,and the decay associated with the direct current component are thecharacteristics used as the basis of said comparison.
 4. A method asclaimed in claim 1, wherein said at least one characteristic of saidunmodified back EMF curve comprises a superimposition of a meanamplitude curve.
 5. A method as claimed in claim 1, wherein said atleast one characteristic of said unmodified back EMF curve comprises thephase and/or change in phase of the oscillating waveform.
 6. A method asclaimed in claim 1, wherein said at least one characteristic of saidunmodified back EMF curve comprises the curves plotted by the peaks ofeither or both of the positive and/or negative portions of theoscillating waveform, and the amplitude of the negative and/or positivepeaks of the oscillating waveform.
 7. A method as claimed in claim 1,wherein said at least one characteristic of said unmodified back EMFcurve comprises the area of the curve beneath the peaks of theoscillating waveform.
 8. A method as claimed in claim 1, wherein said atleast one characteristic of said unmodified back EMF curve comprises thefrequency and/or change in frequency of the oscillating waveform.
 9. Amethod as claimed in claim 1, wherein said at least one characteristicof said unmodified back EMF curve comprises the decay of the peaks ofthe oscillating waveform in a predetermined time.
 10. A method asclaimed in claim 1, wherein said at least one characteristic of saidunmodified back EMF curve comprises a combination of at least twocharacteristics selected from the group consisting of:(a) representationof a superimposition of a mean amplitude curve; (b) representation ofthe phase of the oscillating waveform; (c) representation of the changein phase of the oscillating waveform; (d) representation of the curveplotted by the peaks of the positive portions of the oscillatingwaveform, and the amplitude of those peaks; (e) representation of thecurve plotted by the peaks of the positive portions of the oscillatingwaveform, and the amplitude of the peaks of the negative portions of theoscillating waveform; (f) representation of the curve plotted by thepeaks of the negative portions of the oscillating waveform, and theamplitude of those peaks; (g) representation of the curve plotted by thepeaks of the negative portions of the oscillating waveform, and theamplitude of the peaks of the positive portions of the oscillatingwaveform; (h) representation of the curves plotted by the peaks of boththe positive and the negative portions of the oscillating waveform, andthe amplitude of those peaks; (I) representation of the areas of thecurves beneath the peaks of the oscillating waveform; (j) representationof the frequency of the oscillating waveform; (k) representation of thechange in frequency of the oscillating waveform; (l) representation ofthe frequency and the change in frequency of the oscillating waveform;and (m) representation of the decay of the peaks of the oscillatingwaveform in a predetermined time.
 11. A method of catagorisingcoins/tokens, including the steps of:(a) energising detect coils,between which at least a part of a coin/token is located, with a singlepulse, (b) detecting the back EMF curve of the decaying pulseinformation, (c) analysing the unmodified back EMF curve to extracttherefrom a number of variables and processing those variables toprovide values proportional to the variables, (d) comparing said valuesof said coin/token with a number of reference values to determine intowhich of a number of pre-determined categories said coin token falls;said comparison being made using the formula

    V(t)=Ae.sup.-σt sin (ωt+φ)+Be.sup.-αt

wherein: V(t) is the voltage at time t A is the amplitude of theoscillating waveform B is the amplitude of the direct current componentφ is the phase angle of the response triggering delay ω is 2πƒ ƒ is thefrequency of oscillation σ is the decay associated with the oscillatingwaveform α is the decay associated with the direct current component.12. A method as claimed in claim 11, wherein an indication of thecombined effects of A and B is obtained by integration of the back EMFcurve for an odd number of half-cycles.
 13. A method as claimed in claim11, wherein an indication of the combined effects of σ and α is obtainedby integration of an even number of half-cycles.
 14. A method as claimedin claim 11, wherein an indication of the frequency is obtained by themeasurement of the period for a number of cycles.
 15. A method ofcategorizing coins/tokens, including the steps of:(a) energizing detectcoils, between which at least part of a coin/token is located, with asingle pulse; (b) detecting the back EMF curve of the decaying pulseinformation; (c) analyzing the unmodified back EMF curve to extracttherefrom one or more variables and processing said one or morevariables to provide values proportional to said one or more variables;and (d) comparing said values of said coin/token with at least one of anumber of reference values to determine into which of a number ofpredetermined categories said coin/token falls, wherein said comparisonis made using the formula

    V(t)=Ae.sup.-σt sin (ωt+φ)+Be.sup.-αt

wherein: V(t) is the voltage at time t A is the amplitude of theoscillating wave form B is the amplitude of the direct current componentφ is the phase angle of the response triggering delay ω is 2πƒ ƒ is thefrequency of oscillation σ is the decay associated with the oscillatingwaveform α is the decay associated with the direct current component.16. A method of categorizing coins/tokens, including the steps of:(a)energizing detect coils, between which at least part of a coin/token islocated, with a single pulse; (b) detecting the back EMF curve of thedecaying pulse information; (c) analyzing the unmodified back EMF curveto extract therefrom one or more variables and processing said one ormore variables to provide values proportional to said one or morevariables; and (d) comparing said values of said coin/token with atleast one of a number of reference values to determine into which of anumber of predetermined categories said coin/token falls, wherein thestep of analyzing the unmodified back EMF curve comprises the stepsof:comparing said unmodified back EMF curve to a reference unmodifiedback EMF curve; and determining said values by calculating thedifference of said one or more variables between said unmodified backEMF curve and said reference unmodified back EMF curve.